For a long time, running short on fuel has been a concern typically restricted to situations where a driver is distant from any gas stations, in what are normally remote areas. With the prevalence of refueling points available in most populated areas, as long as a driver shows even a modicum of caution with regards to a low fuel state, a vehicle should almost never run out of gas.
The introduction of battery electric vehicles (BEVs), however, has changed all that. First, BEVs take significantly more time than gas-powered vehicles to refuel. While a gas powered vehicle can often be fully refueled in less than five minutes, fully charging a BEV could take an hour or more. Accordingly, people will generally prefer to refuel the vehicle during “down time,” such as when it is parked in a garage and not in use.
Additionally, there are not nearly as many electric “gas stations” as gasoline providing gas stations. In other words, if a person finds they are low on power in a BEV while underway, it is far more difficult to mitigate the situation. Short of pulling into someone's driveway and asking if they can recharge for a bit, there is little a person running critically low on power can do. Because of this, fear of running out of power is one of the number one concerns of the electric car owner.
Automotive manufacturers recognize this concern and the lack of recharging options, and accordingly they will often provide some form of range estimation. Based on a variety of factors, the range estimation will hopefully serve to offer a driver some indication of how far the vehicle can travel before the power runs out.